1. Field of the Invention
The invention relates to a sealing apparatus for a submersible electric motor, and particularly a motor employed to drive a pump in a subterranean well.
2. History of the Prior Art
Electric motors have long been utilized to pump well fluids from subterranean wells. Normally, the motor and pump are located at substantial distances below the surface and are surrounded by well fluids. Since the well fluids to be pumped must penetrate the housing of the pump, it is unavoidable that the well fluids will come into contact with the shaft connecting the electric motor and the driven pump. Shaft seals in a large variety of configurations have been employed to prevent the leakage of well fluids downwardly along the shaft and into the motor housing, thus destroying the electrical insulation necessarily provided for the motor windings. Additionally, it is common practice to fill the interior of the motor housing with a high dielectric protective oil and this same oil has been provided in surrounding relationship to the shaft seals and bearings to absorb heat that is necessarily developed in the normal operation of the motor. When such protective fluid is employed, care must be taken to equalize the pressure of the confined protective fluid with that of the well fluids surrounding the motor for the reason that the existence of a substantial pressure differential in either direction will greatly contribute to leakage of the protective fluid of the motor enclosure, or worse, leakage of the well fluids into the motor housing.
To provide such pressure equalization, the prior art has resorted to the use of diaphragms which are disposed intermediate the motor protective fluid and the well fluid to achieve constant equalization of pressures therebetween through the expansion or contraction of the flexible diaphragm. Even this precaution does not preclude eventual leakage of well fluids into the interior of the motor housing resulting in a substantial reduction in the useful life of the downhole electric motor.